Ultrasound transducer with enhanced thermal conductivity

ABSTRACT

A composite structure of a backing material with enhanced conductivity for use in a transducer is presented. The composite structure includes a plurality of layers of backing material alternatingly arranged with a plurality of thermal conductive elements, wherein the plurality of thermal conductive elements are configured to transfer heat from a center of the transducer to a plurality of points on the composite structure of backing material.

BACKGROUND

The invention relates generally to transducers, and more specifically totransducers with increased thermal conductivity.

Transducers, such as acoustic transducers, have found application inmedical imaging wherein an acoustic probe is held against a patient andthe probe transmits and receives ultrasound waves, which in turn mayfacilitate the imaging of the internal tissues of the patient. It may beadvantageous to operate the acoustic probe at a maximum permissibleacoustic intensity to enable higher quality imaging, which may beachieved via better penetration of the acoustic waves into the patient'stissues. However, operating the acoustic probe at higher acousticintensities may disadvantageously result in the production of excessiveheat in the transducer assembly.

Moreover, there exist limits on the maximum external temperature of anacoustic probe at points of contact with the patient and a technician.Furthermore, in certain modes of operation of the acoustic probe, theheat generated within the transducer elements or within the transducerassembly may cause the temperature of some regions of the probe surfaceto exceed permissible limits. However, as will be appreciated by oneskilled in the art, materials typically employed to fabricate thetransducer elements are primarily selected based upon their acousticproperties, and are generally known to possess relatively low thermalconductivity. Furthermore, the transducer elements are generallyisolated from one another by dicing kerfs that provide additionalthermal insulation of the transducer elements. Hence, the heat generatedwithin the transducer elements is trapped in the acoustic stack causingthe face temperature of the probe to rise above the ambient temperature.It may be advantageous to dissipate the heat that may be trapped in thearray of transducer elements in order to circumvent the overheating ofthe patient contact surfaces of the transducer assembly.

Transducer assemblies are generally fabricated employing materials withlower intrinsic thermal conductivity. The low thermal conductivity oftransducer assemblies may result in the overheating of the probe.Disadvantageously, many previous attempts to enhance the thermalconductivity of the acoustic probe have had limited effect on the facetemperature of the probe and therefore may be ineffective insufficiently reducing the face temperature enough to prevent discomfortto a patient. Other prior techniques have been more successful atsufficiently reducing face temperature of the probe, but thisimprovement often comes at the expense of the acoustic performance ofthe transducer assembly.

It would be desirable draw the heat away from the heat-generating regionof the transducer assembly to lower the face temperature of theultrasound probe to an acceptable level. Further, it would be desirableto lower the face temperature of the probe to facilitate the operationof the probe at a higher transmit power thereby yielding improvements indiagnostic imaging.

BRIEF DESCRIPTION

Briefly, in accordance with an exemplary embodiment of the presenttechnique, a composite structure of a backing material for use in atransducer is presented. The composite structure includes a plurality oflayers of backing material alternatingly arranged between a plurality ofthermal conductive elements, wherein the plurality of thermal conductiveelements are configured to transfer heat from a center of the transducerto a plurality of points on the composite structure of backing material.

According to a further embodiment of the present technique, a transducerassembly including a composite structure of backing material ispresented. The transducer assembly includes a plurality of transducerelements disposed in a first layer having a first front face and a firstrear face. Furthermore, the composite structure includes an absorberdisposed in a second layer having a second front face and a second rearface, wherein the absorber is disposed adjacent to the first rear face,and is acoustically coupled to the first rear face, and wherein theabsorber includes a composite structure of backing material havingconductive elements dispersed therethrough.

In accordance with another embodiment of the present technique, a methodfor forming a composite structure of backing material for use in atransducer assembly is presented. The method includes dicing a block ofbacking material to form a plurality of layers of backing material.Furthermore, the method includes alternatingly disposing the pluralityof layers of backing material between a plurality of thermal conductiveelements to form the composite structure of backing material.

According to a further aspect of the present technique, an alternatemethod for forming a composite structure of backing material for use ina transducer assembly is presented. The method includes arranging aplurality of thermal conductive elements in a spaced relationship in amold. Additionally, the method includes casting an absorber materialaround the plurality of thermal conductive elements to form thecomposite structure of backing material.

In accordance with a further aspect of the present technique, a methodof manufacturing a transducer assembly is presented. The method includesdisposing a plurality of acoustic transducer elements in a first layerhaving a first front face and a first rear face. Furthermore, the methodincludes providing a backing comprising an absorber disposed in a secondlayer having a second front face and a second rear face, wherein theabsorber is disposed adjacent to the first rear face and is acousticallycoupled to the first rear face, and wherein the absorber includes acomposite structure of backing material having conductive elementsdispersed therethrough.

According to yet another aspect of the present technique, an ultrasoundsystem including a composite structure of backing material is presented.The system includes an acquisition subsystem configured to acquireultrasound data, wherein the acquisition subsystem includes at least onetransducer assembly, wherein the transducer assembly includes acomposite structure of backing material having conductive elementsdispersed therethrough. Additionally, the system includes a processingsubsystem configured to process the ultrasound data acquired via theacquisition subsystem.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a diagrammatic illustration of an ultrasound system;

FIG. 2 is a perspective view of a transducer assembly;

FIG. 3 is a cross-sectional side view of a cut away of the transducerassembly of FIG. 2 along cross-sectional line 3—3;

FIG. 4 is a perspective view illustrating an exemplary embodiment of astacked composite structure of backing material with enhanced thermalconductivity for use in a transducer assembly according to aspects ofthe present technique;

FIG. 5 is a flow chart depicting steps for forming a composite structureof backing material according to aspects of the present technique; and

FIG. 6 is a flow chart depicting steps of an alternate method forforming a composite structure according to further aspects of thepresent technique.

DETAILED DESCRIPTION

In many fields, such as medical imaging, transducer materials chosen fortheir acoustic properties typically possess lower thermal conductivity.Additionally, the individual transducer elements are often separatedfrom one another by dicing kerfs that provide additional thermalinsulation. Therefore, heat generated within the transducer assembly maybe trapped within the transducer assembly thereby causing the facetemperature of the transducer assembly to increase above permissiblelimits. It may be desirable to enhance the thermal conductivity of thetransducer assembly, while maintaining the acoustic properties of thetransducer assembly. The techniques discussed herein address some or allof these issues.

FIG. 1 is a block diagram of an embodiment of an ultrasound system 10.The ultrasound system includes an acquisition subsystem 12 and aprocessing subsystem 14. The acquisition subsystem 12 includes atransducer array 18 (having a plurality of transducer array elements),transmit/receive switching circuitry 20, a transmitter 22, a receiver24, and a beamformer 26. The processing subsystem 14 includes a controlprocessor 28, a demodulator 30, an imaging mode processor 32, a scanconverter 34 and a display processor 36. The display processor 36 isfurther coupled to a display monitor 38 for displaying images. Userinterface 40 interacts with the control processor 28 and the displaymonitor 38. The control processor 28 may also be coupled to a remoteconnectivity subsystem 42 including a web server 44 and a remoteconnectivity interface 46. The processing subsystem 14 may be furthercoupled to a data repository 48 configured to receive ultrasound imagedata. The data repository 48 interacts with image workstation 50.

The aforementioned components may be dedicated hardware elements such ascircuit boards with digital signal processors or may be software runningon a general-purpose computer or processor such as a commercial,off-the-shelf personal computer (PC). The various components may becombined or separated according to various embodiments of the invention.Thus, those skilled in the art will appreciate that the presentultrasound system 10 is provided by way of example, and the presenttechniques are in no way limited by the specific system configuration.

In the acquisition subsystem 12, the transducer array 18 is in contactwith a patient or subject 16. The transducer array is coupled to thetransmit/receive (T/R) switching circuitry 20. The T/R switchingcircuitry 20 is coupled to the output of transmitter 22 and the input ofthe receiver 24. The output of the receiver 24 is an input to thebeamformer 26. The beamformer 26 is further coupled to the input of thetransmitter 22 and to the input of the demodulator 30. The beamformer 26is also coupled to the control processor 28 as shown in FIG. 1.

In the processing subsystem 14, the output of demodulator 30 is coupledto an input of an imaging mode processor 32. The control processor 28interfaces with the imaging mode processor 32, the scan converter 34 andthe display processor 36. An output of imaging mode processor 32 iscoupled to an input of scan converter 34. An output of the scanconverter 34 is coupled to an input of the display processor 36. Theoutput of display processor 36 is coupled to the monitor 38.

The ultrasound system 10 transmits ultrasound energy into the subject 16and receives and processes backscattered ultrasound signals from thesubject 16 to create and display an image. To generate a transmittedbeam of ultrasound energy, the control processor 28 sends command datato the beamformer 26 to generate transmit parameters to create a beam ofa desired shape originating from a certain point at the surface of thetransducer array 18 at a desired steering angle. The transmit parametersare sent from the beamformer 26 to the transmitter 22. The transmitter22 uses the transmit parameters to properly encode transmit signals tobe sent to the transducer array 18 through the T/R switching circuitry20. The transmit signals are set at certain levels and phases withrespect to each other and are provided to individual transducer elementsof the transducer array 18. The transmit signals excite the transducerelements to emit ultrasound waves with the same phase and levelrelationships. As a result, a transmitted beam of ultrasound energy isformed in a subject 16 within a scan plane along a scan line when thetransducer array 18 is acoustically coupled to the subject 16 by using,for example, ultrasound gel. The process is known as electronicscanning.

The transducer array 18 is a two-way transducer. When ultrasound wavesare transmitted into a subject 16, the ultrasound waves arebackscattered off the tissue and blood samples within the subject 16.The transducer array 18 receives the backscattered waves at differenttimes, depending on the distance into the tissue they return from andthe angle with respect to the surface of the transducer array 18 atwhich they return. The transducer elements convert the ultrasound energyfrom the backscattered waves into electrical signals.

The electrical signals are then routed through the T/R switchingcircuitry 20 to the receiver 24. The receiver 24 amplifies and digitizesthe received signals and provides other functions such as gaincompensation. The digitized received signals corresponding to thebackscattered waves received by each transducer element at various timespreserve the amplitude and phase information of the backscattered waves.

The digitized signals are sent to the beamformer 26. The controlprocessor 28 sends command data to beamformer 26. The beamformer 26 usesthe command data to form a receive beam originating from a point on thesurface of the transducer array 18 at a steering angle typicallycorresponding to the point and steering angle of the previous ultrasoundbeam transmitted along a scan line. The beamformer 26 operates on theappropriate received signals by performing time delaying and focusing,according to the instructions of the command data from the controlprocessor 28, to create received beam signals corresponding to samplevolumes along a scan line in the scan plane within the subject 16. Thephase, amplitude, and timing information of the received signals fromthe various transducer elements is used to create the received beamsignals.

The received beam signals are sent to the processing subsystem 14. Thedemodulator 30 demodulates the received beam signals to create pairs ofI and Q demodulated data values corresponding to sample volumes withinthe scan plane. Demodulation is accomplished by comparing the phase andamplitude of the received beam signals to a reference frequency. The Iand Q demodulated data values preserve the phase and amplitudeinformation of the received signals.

The demodulated data is transferred to the imaging mode processor 32.The imaging mode processor 32 uses parameter estimation techniques togenerate imaging parameter values from the demodulated data in scansequence format. The imaging parameters may include parameterscorresponding to various possible imaging modes such as B-mode, colorvelocity mode, spectral Doppler mode, and tissue velocity imaging mode,for example. The imaging parameter values are passed to the scanconverter 34. The scan converter 34 processes the parameter data byperforming a translation from scan sequence format to display format.The translation includes performing interpolation operations on theparameter data to create display pixel data in the display format.

The scan converted pixel data is sent to the display processor 36 toperform any final spatial or temporal filtering of the scan convertedpixel data, to apply grayscale or color to the scan converted pixeldata, and to convert the digital pixel data to analog data for displayon the monitor 38. The user interface 40 is coupled to the controlprocessor 28 to allow a user to interface with the ultrasound system 10based on the data displayed on the monitor 38.

FIG. 2 illustrates a perspective side view of a transducer assembly 52.Typically, the transducer assembly 52, for example, an acoustictransducer assembly, as illustrated in FIG. 2, may include one or moretransducer elements (not shown), one or more matching layers (not shown)and a lens 54. The transducer elements may be arranged in a spacedrelationship, such as, but not limited to, an array of transducerelements disposed on a layer, wherein each of the transducer elementsmay include a transducer front face and a transducer rear face. As willbe appreciated by one skilled in the art, the transducer elements may befabricated employing materials, such as, but not limited to leadzirconate titanate (PZT), polyvinylidene difluoride (PVDF) and compositePZT. The transducer assembly 52 may also include one or more matchinglayers disposed adjacent to the front face of the array of transducerelements, wherein each of the matching layers may include a matchinglayer front face and a matching layer rear face. The matching layersfacilitate the matching of an impedance differential that may existbetween the high impedance transducer elements and a low impedancepatient or subject 16 (see FIG. 1). The lens 54 may be disposed adjacentto the matching layer front face and provides an interface between thepatient and the matching layer.

Additionally, the transducer assembly 52 may include a backing layer 56,having a front face and a rear face, that may be fabricated employing asuitable acoustic damping material possessing high acoustic losses. Thebacking layer 56 may be acoustically coupled to the rear face of thearray of transducer elements, wherein the backing layer 56 facilitatesthe attenuation of acoustic energy that may emerge from the rear face ofthe array of transducer elements.

Furthermore, the transducer assembly 52 may also include a support plate58 configured to provide support to the transducer assembly 52 includingthe lens 54, the matching layers and the backing layer 56. The supportplate 58 may include a T-shaped support plate, as illustrated in FIG. 2.Also, the support plate 58 may be coupled to the rear face of thebacking layer 56. As will be appreciated by one skilled in the art, thesupport plate 58 may be fabricated employing metals such as, but notlimited to, aluminum. Furthermore, a central plate 59 may be coupled tothe support plate 58. The central plate 59 may facilitate thedissipation of heat as will be described hereinafter. Circuitry 60, suchas flexible printed circuits, that may for example include copper signaland ground conductors on a polyimide substrate, may be disposed on thecentral plate 59. Additionally, as illustrated in FIG. 2, a split groundplane 62 facilitates the separation of the transmitting and receivingregions of the transducer assembly 52.

Moreover, the transducer assembly 52 may also include an electricalshield 64 that facilitates the isolation of the transducer elements fromthe external environment. The electrical shield may include metal foils,wherein the metal foils may be fabricated employing metals such as, butnot limited to, copper, aluminum, brass, and gold.

FIG. 3 illustrates a cross-sectional side view 66 of a cut away of thetransducer assembly 52 of FIG. 2 along cross-sectional line 3—3. Asillustrated in FIG. 3, the cross-sectional side view 66 of thetransducer assembly 52 of FIG. 2 includes the backing layer 56.Furthermore, the transducer assembly also includes the support plate 58.The array of transducer elements 68 is disposed adjacent to the frontface of the backing layer 56. In addition, a first matching layer 70,having a first front face and a first rear face, may be positionedadjacent to the front face of the array of transducer elements 68. Also,as illustrated in FIG. 3, a second matching layer 72, having a secondfront face and a second rear face may be disposed adjacent to the firstfront face of the first matching layer 70. Furthermore, the lens 54 maybe disposed adjacent to the front face of the second matching layer 72.As will be appreciated by one skilled in the art, the lens 54 mayinclude a portion configured to cover the array of transducer elements68 and the matching layers 70, 72, as illustrated in FIG. 3.

As mentioned hereinabove, the transducer assembly 52 (see FIG. 2)includes a backing layer 56. FIG. 4 illustrates an exemplary compositestructure 74 of the backing layer 56 that facilitates the dissipation ofthe heat that may be trapped in the central region of the transducerassembly 52. The central region may include the array of transducerelements 68, the first matching layer 70, the second matching layer 72and the lens 54 (see FIG. 3). By implementing the backing layer 56having a composite structure 74, the acoustic performance of thetransducer assembly 52 may be advantageously enhanced. In accordancewith an embodiment of the present technique, the heat that may betrapped in a central region of the transducer assembly 52 may bedissipated via the composite structure 74 that is coupled to the rearface of the array of transducer elements 68. For example, the heat fromthe central region of the transducer assembly 52 may be dissipated to aplurality of sides and/or a rear side of the composite structure 74. Aswill be appreciated by one skilled in the art, the backing layer 56 isfabricated employing materials that exhibit desirable acousticproperties. For example, the backing layer 56 may be fabricatedemploying material, such as, but not limited to, a composite of epoxy,tungsten particles and small silicone spheres. However, such materialstypically exhibit low thermal conductivity. For example the thermalconductivity of the backing material varies in a range of about 0.2Watts/meter/Kelvin (W/m/K) to about 0.4 W/m/K. Hence, altering theproperties of the backing layer 56 to enhance the thermal conductivitymay disadvantageously lead to deterioration of the performance of thetransducer assembly 52.

According to one aspect of the present technique, the thermalconductivity of the backing layer 56 may be advantageously enhanced byintroducing a material possessing high thermal conductivity to form acomposite structure 74 of backing material while maintaining theacoustic properties of the backing layer 56. FIGS. 4–6 illustrate anexemplary structure and methods for forming the composite structure 74of the backing layer 56 of FIG. 2, according to exemplary embodiments ofthe present technique. In a presently contemplated configuration, thecomposite structure 74 of backing material includes alternating layersof backing material and thermally conductive elements. FIG. 4 is adiagrammatical view of an embodiment of the stacked composite structure74 of backing material. The composite structure 74 includes aarrangement wherein layers of backing material 76 are alternativelystacked with layers of material possessing high thermal conductivity 78(hereinafter referred to as thermal conductive elements 78).

In accordance with an exemplary embodiment of the present technique, aflow chart illustrating a method for forming the composite structure 74of backing material of FIG. 4 is provided with reference to FIG. 5. Asillustrated in FIG. 5, a block of backing material, as depicted in block82, may be employed to form the composite structure 74 of backingmaterial with enhanced thermal conductivity. The method for forming thecomposite structure 74 begins at step 84, where the block of backingmaterial 82 is diced to form a plurality of backing material layers 76(see FIG. 4). The thickness of the backing material layers 76 may varyin a range from about 0.2 mm to about 2.0 mm.

At step 86, the backing material layers 76 are stacked in anarrangement, wherein the backing material layers 76 are alternativelystacked with layers of material of high thermal conductivity 78 (thermalconductive elements 78). The thermal conductive elements 78 may includea metal foil, wherein the metal foil may include, for example, a copperfoil, an aluminum foil, and alloys or combinations thereof. However, onthe other hand, the thermal conductive elements may include highlyconductive non-metals, such as, but not limited to, a pyrolytic graphiteor a boron nitride. The thickness of the thermal conductive elements 78,such as the metal foil, may vary in a range from about 0.01 mm to about0.04 mm. Once stacked, the pitch between the thermal conductive elements78 may vary in a range from about 0.2 mm to about 2.0 mm. Alternatively,the thermal conductive elements 78 may comprise a material with highthermal conductivity in the form of wires, rods, flexible circuittraces, flexible circuit ground planes, and combinations thereof. In apresently contemplated configuration of the present technique, in orderto achieve an acoustically uniform attenuating medium, it may beadvantageous to limit the thickness of the thermal conductive elements78 to be significantly lower than a wavelength of sound at an operatingfrequency of the transducer assembly 52. In addition, the number ofthermal conductive elements 78 that may be included in the compositestructure 74 may be chosen such that the thermal conductivity of thecomposite structure 74 is advantageously enhanced while havingnegligible effect on the acoustic properties of the composite structure74.

Additionally, in accordance with an exemplary embodiment of the presenttechnique, the pitch between the thermal conductive elements 78 may bevaried with respect to one another based upon a location in thetransducer assembly 52. As will be appreciated by one skilled in theart, the central region of the transducer assembly 52 is aheat-generating region. Hence, a higher density of thermal conductiveelements 78 may be disposed in the central region of the transducerassembly 52, while a lower density of thermal conductive elements 78 maybe disposed in a peripheral region of the transducer assembly 52,thereby resulting in reduced fabrication cost.

Furthermore, as illustrated in FIG. 2, the ground plane 62 may be splitto provide increased isolation between a transmitting region and areceiving region of the transducer assembly 52. According to anexemplary embodiment of the present technique, separate sets of thermalconductive elements 78 may be employed for the transmitting andreceiving regions of the transducer assembly 52, thereby resulting inthe reduction of noise and crosstalk levels.

As previously discussed, it may be desirable to enhance the thermalconductivity of the backing material by introducing a material of highthermal conductivity while maintaining the acoustic properties of thebacking material. In a presently contemplated configuration, a totalvolume of the thermal conductive elements 78 may be less thanapproximately 5 volume percent of a volume of the backing material.Further, it may be advantageous to limit the total volume of the thermalconductive elements 78 to less than approximately 3 volume percent ofthe volume of the backing material.

In addition, it may be advantageous to directionally align the thermalconductive elements 78 with the backing material layers 76 to facilitatethe efficient dissipation of heat from the transducer assembly 52. Forexample, the thermal conductive elements 78 may be disposed in adirection parallel to the direction of the backing material layers 76 toadvantageously enhance the thermal conductivity of the compositestructure 74. Furthermore, in accordance with an exemplary embodiment ofthe present technique, the thermal conductive elements 78 may bedisposed in the composite structure 74 such that they extend through thecomposite structure from the heat-generating region of the transducerassembly 52 to heat sinks (not shown) or other thermal conductiveelements 78 that may be positioned on a periphery of the compositestructure 74. As will be appreciated by one skilled in the art, theheat-generating region of the transducer assembly 52 may include thetransducer elements 68, the matching layers 70, 72 and the lens 54 (seeFIG. 3). Additionally, the thermal conductive elements may bedistributed throughout the composite structure 74 to facilitateminimizing any thermal resistance that may be present between a heatsource point and a heat sink.

Returning to FIG. 5, at step 88, the stacked alternating layers ofbacking material 76 and thermal conductive elements 78 may be bonded toform the composite structure 74 of backing material. Furthermore, atstep 90, the composite structure may be machined to form a predeterminedshape of backing material to yield a composite structure 74 of backingmaterial as depicted in block 92. For example, the composite structuremay be machined to form a rectangular block having one faceapproximately equivalent to the size of the transducer array 68 (seeFIG. 3).

According to an alternate embodiment of the present technique, thermalconductive elements 78 may be directly deposited onto the backingmaterial layers 76. The backing material layers 76 may be subsequentlybonded together to form the composite structure 74 of backing material.

FIG. 6 is a flow chart depicting an alternate method of forming thecomposite structure 74 of backing material, according to further aspectsof the present technique. As suggested by the method summarized in FIG.6, the thermal conductive elements 78, depicted in block 94, may beemployed to form the composite structure 74 of backing material withenhanced thermal conductivity. Given the thermal conductive elements 78,the method for forming the composite structure begins at step 96, wherethe thermal conductive elements 78 may be arranged in a spacedrelationship, wherein the spaced relationship may include apredetermined pattern. For example, the predetermined pattern mayinclude parallel sheets of the thermal conductive elements positioned ata uniform pitch. Alternatively, the predetermined pattern may include atwo dimensional (2D) array of thermal conductive elements 78, such asrods and strips, placed at a uniform pitch. Furthermore, the thermalconductive elements 78 that have been arranged in a spaced relationshipmay be disposed in a mold. At step 98, the backing material may be castaround the thermal conductive elements 78 to form the compositestructure 74 of backing material. In addition, at step 100, thecomposite structure may be machined to form a predetermined shape ofbacking material to yield a composite structure 74 of backing materialas depicted in block 102. As previously described the compositestructure may be machined to form a rectangular block having one faceapproximately equivalent to the size of the transducer array 68 (seeFIG. 3).

The composite structure 74 of backing material formed employing methodsdescribed hereinabove may be employed in an ultrasound system asillustrated in FIG. 1.

As mentioned hereinabove, the plurality of thermal conductive elements78 that may be included in the composite structure 74 of backingmaterial facilitate the transfer of heat from the center of thetransducer assembly to a plurality of points on the composite structure74 of backing material. For example, the points of heat dissipation onthe composite structure 74 of backing material may include one or moresides of the composite structure 74. Additionally, the points of heatdissipation may include a rear side of the composite structure 74.

Furthermore, in accordance with an exemplary embodiment of the presenttechnique, a thermal conductive structure, such as the central plate 59(see FIG. 2), configured to provide a thermal path for the transfer ofheat away from the plurality of points on the composite structure 74 ofbacking material of the transducer assembly 52, is presented. Forexample, the thermal conductive structure 59 may be employed to providea thermal path to transfer the heat away from the heat-generating regionof the transducer assembly 52 via the composite structure 74 toward arear region of a probe. The heat may then be dissipated into thesurrounding air, thereby facilitating the reduction of temperature ofthe patient contact area. Alternatively, an active cooling mechanism maybe employed to transfer the heat away from the heat-generating region ofthe transducer assembly 52 via the composite structure 74 of backingmaterial. For example, the active cooling mechanism may include a heattransducer cooling arrangement that facilitates the removal of heatemploying coolants.

The composite structure 74 of backing material described hereinabove,advantageously enables the efficient dissipation of heat from theheat-generating region of the transducer assembly 52. The thermalconductivity of the backing material that is in direct contact with theheat-generating region may be advantageously enhanced by theintroduction of thermal conductive elements 78 that facilitate thetransfer of heat from the heat-generating region to other regions of thetransducer assembly.

Thus the effective dissipation of heat from the transducer assemblyenables the reduction of ultrasound face temperature thereby allowingthe probe to be operated at a higher transmit power yielding significantimprovements in diagnostic imaging. Furthermore, the methods for formingthe composite structure 74 of backing material minimize changes to theacoustic properties of the backing material thereby enhancing theperformance of the transducer assembly 52.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. A composite structure of a backing material for use in a transducer,the composite structure comprising: a plurality of layers of backingmaterial alternatingly arranged between a plurality of thermalconductive elements, wherein the plurality of thermal conductiveelements are configured to transfer heat from a center of the transducerto a plurality of points on the composite structure of backing material,and wherein a volume of the thermal conductive elements comprises up toabout 5 volume percent of a volume of the backing material.
 2. Thecomposite structure of claim 1, wherein the plurality of layers ofbacking material and the plurality of thermal conductive elements arebonded to form the composite structure.
 3. The composite structure ofclaim 1, wherein the plurality of thermal conductive elements isdisposed parallel to the plurality of layers of backing material.
 4. Thecomposite structure of claim 1, wherein the plurality of points on thecomposite structure of backing material comprises one or more sides ofthe composite structure of backing material.
 5. The composite structureof claim 1, wherein the plurality of points on the composite structureof backing material comprises a rear side of the composite structure ofbacking material.
 6. The composite structure of claim 1, wherein thebacking material comprises an epoxy material.
 7. The composite structureof claim 1, wherein a thickness of each of the plurality of layers ofbacking material is in a range from about 0.2 mm to about 2.0 mm.
 8. Thecomposite structure of claim 1, wherein the plurality of thermalconductive elements comprises a metal foil.
 9. The composite structureof claim 8, wherein the metal foil is selected from the group consistingof a copper foil, an aluminum foil, and alloys or combinations thereof.10. The composite structure of claim 1, wherein the plurality of thermalconductive elements comprises a conductive non-metal.
 11. The compositestructure of claim 10, wherein the conductive non-metal comprises atleast one of a pyrolytic graphite and a boron nitride.
 12. The compositestructure of claim 1, wherein the plurality of thermal conductiveelements is selected from the group consisting of wires, rods, flexiblecircuit traces, and combinations thereof.
 13. The composite structure ofclaim 1, wherein a thickness of the plurality of thermal conductiveelements is in a range from about 0.01 mm to about 0.04 mm.
 14. Thecomposite structure of claim 1, wherein a pitch between thermalconductive elements in the composite structure is in a range of about0.2 mm to about 2.0 mm.
 15. The composite structure of claim 1, whereinthe plurality of thermal conductive elements is more dense at a centralarea of the transducer than at a peripheral area of the transducer. 16.A transducer assembly comprising: a plurality of transducer elementsdisposed in a first layer having a first front face and a first rearface; and an absorber disposed in a second layer having a second frontface and a second rear face, wherein the absorber is disposed adjacentto the first rear face and is acoustically coupled to the first rearface, and wherein the absorber comprises a composite structure ofbacking material having thermal conductive elements dispersedtherethrough, and wherein a volume of the thermal conductive elementscomprises up to about 5 volume percent of a volume of the backingmaterial.
 17. The assembly of claim 16, further comprising a thermalconductive structure coupled to the composite structure of backingmaterial, wherein the thermal conductive structure is configured toprovide a thermal path from the composite structure of backing materialto a heat dissipating structure.
 18. The assembly of claim 17, whereinthe thermal conductive structure comprises a metal sheet extending froma plurality of sides of the composite structure to an inside surface ofa probe handle.
 19. The assembly of claim 18, wherein the metal sheetcomprises a copper sheet.
 20. The assembly of claim 17, wherein thethermal conductive structure comprises a cooling system, wherein thecooling system is configured to transfer heat from the compositestructure to a heat dissipating structure via a transducer cable. 21.The assembly of claim 16, wherein the composite structure of backingmaterial comprises a plurality of layers of backing materialalternatingly arranged between a plurality of thermal conductiveelements, wherein the plurality of thermal conductive elements areconfigured to transfer heat from a center of the transducer to aplurality of points on the composite structure of backing material. 22.The assembly of claim 21, wherein the plurality of layers of backingmaterial and the plurality of thermal conductive elements are bonded toform the composite structure.
 23. The assembly of claim 21, wherein theplurality of thermal conducting elements is disposed parallel to theplurality of layers of backing material.
 24. The assembly of claim 21,wherein the plurality of points on the composite structure of backingmaterial comprises one or more sides of the composite structure ofbacking material.
 25. The assembly of claim 21, wherein the plurality ofpoints on the composite structure of backing material comprises a rearside of the composite structure of backing material.
 26. The assembly ofclaim 21, wherein the backing material comprises an epoxy material. 27.The assembly of claim 26, wherein a thickness of each of the pluralityof layers of backing material is in a range from about 0.2 mm to about2.0 mm.
 28. The assembly of claim 21, wherein the plurality of thermalconductive elements comprises a metal foil.
 29. The assembly of claim28, wherein the metal foil is selected from the group consisting of acopper foil, an aluminum foil, and alloys or combinations thereof. 30.The assembly of claim 21, wherein the plurality of thermal conductiveelements comprises a conductive non-metal.
 31. The assembly of claim 30,wherein the conductive non-metal comprises at least one of a pyrolyticgraphite and a boron nitride.
 32. The assembly of claim 21, wherein theplurality of thermal conductive elements is selected from the groupconsisting of wires, rods, flexible circuit traces, and combinationsthereof.
 33. The assembly of claim 21, wherein a pitch between thermalconductive elements in the composite structure is in a range of about0.2 mm to about 2.0 mm.
 34. The assembly of claim 21, wherein theplurality of thermal conductive elements is more dense at a central areaof the transducer than at a peripheral area of the transducer.
 35. Theassembly of claim 21, wherein a thickness of the plurality of thermalconductive elements is in a range from about 0.01 mm to about 0.04 mm.36. The assembly of claim 16, comprising a metal foil that is configuredto provide electrical shielding to the plurality of transducer elements.37. An ultrasound system, the system comprising: an acquisitionsubsystem configured to acquire ultrasound data, wherein the acquisitionsubsystem comprises at least one transducer assembly, wherein thetransducer assembly comprises a composite structure of backing materialhaving thermal conductive elements dispersed therethrough, and wherein avolume of the thermal conductive elements comprises up to about 5 volumepercent of a volume of the backing material; and a processing subsystemconfigured to process the ultrasound data acquired via the acquisitionsubsystem.
 38. The ultrasound system of claim 37, wherein theacquisition subsystem comprises at least one transducer assemblyconfigured to facilitate the acquisition of the ultrasound data.
 39. Theultrasound system of claim 38, wherein the at least one transducerassembly comprises a plurality of transducer elements disposed in afirst layer having a first front face and a first rear face, an absorberdisposed in a second layer having a second front face and a second rearface, wherein the absorber is disposed adjacent to the first rear face,and wherein the absorber comprises a composite structure of backingmaterial having conductive elements dispersed therethrough.
 40. Theultrasound system of claim 39, further comprising a disposing a thermalconductive structure, wherein the thermal conductive structure isconfigured to provide a thermal path from the composite structure ofbacking material to a heat dissipating structure.
 41. The ultrasoundsystem of claim 40, wherein the thermal conductive structure comprises ametal sheet extending from a plurality of sides of the compositestructure to an inside surface of a probe handle.
 42. The ultrasoundsystem of claim 41, wherein the metal sheet comprises a copper sheet.43. The ultrasound system of claim 40, wherein the thermal conductivestructure comprises a cooling system, wherein the cooling system isconfigured to transfer heat from the composite structure to a heatdissipating structure via a transducer cable.
 44. The ultrasound systemof claim 39, wherein the absorber comprises a plurality of layers ofbacking material alternatingly arranged between a plurality of thermalconductive elements, wherein the plurality of thermal conductiveelements are configured to transfer heat from a center of the transducerto a plurality of points on the composite structure of backing material.45. The ultrasound system of claim 44, wherein the plurality of layersof backing material and the plurality of thermal conductive elements arebonded to form the composite structure.
 46. The ultrasound system ofclaim 44, wherein the plurality of thermal conducting elements isdisposed parallel to the plurality of layers of backing material. 47.The ultrasound system of claim 44, wherein the plurality of points onthe composite structure of backing material comprises one or more sidesof the composite structure of backing material.
 48. The ultrasoundsystem of claim 44, wherein the plurality of points on the compositestructure of backing material comprises a rear side of the compositestructure of backing material.
 49. The ultrasound system of claim 44,wherein the backing material comprises an epoxy material.
 50. Theultrasound system of claim 44, wherein a thickness of each of theplurality of layers of backing material is in a range from about 0.2 mmto about 2.0 mm.
 51. The ultrasound system of claim 44, wherein theplurality of thermal conductive elements comprises a metal foil.
 52. Theultrasound system of claim 51, wherein the metal foil is selected fromthe group consisting of a copper foil, an aluminum foil, and alloys orcombinations thereof.
 53. The ultrasound system of claim 44, wherein theplurality of thermal conductive elements comprises a conductivenon-metal.
 54. The ultrasound system of claim 53, wherein the conductivenon-metal comprises at least one of a pyrolytic graphite and a boronnitride.
 55. The ultrasound system of claim 44, wherein the plurality ofthermal conductive elements is selected from the group consisting ofwires, rods, flexible circuit traces, and combinations thereof.
 56. Theultrasound system of claim 44, wherein a pitch between thermalconductive elements in the composite structure is in a range of about0.2 mm to about 2.0 mm.
 57. The ultrasound system of claim 44, wherein athickness of the plurality of thermal conductive elements is in a rangefrom about 0.01 mm to about 0.04 mm.
 58. The ultrasound system of claim44, wherein the plurality of thermal conductive elements is more denseat a central area of the transducer than at a peripheral area of thetransducer.
 59. The ultrasound system of claim 37, comprising a displaymodule configured to display the processed ultrasound data.
 60. Theultrasound system of claim 37, comprising a user interface configured toenable an operator to acquire and/or display the ultrasound data. 61.The ultrasound system of claim 37, comprising a data repository moduleconfigured to store the ultrasound data.
 62. The ultrasound system ofclaim 37, comprising an imaging workstation module configured tomanipulate the ultrasound data.
 63. A composite structure of a backingmaterial for use in a transducer, the composite structure comprising: aplurality of layers of backing material alternatingly arranged between aplurality of thermal conductive elements, wherein the plurality ofthermal conductive elements are configured to transfer heat from acenter of the transducer to a plurality of points on the compositestructure of backing material, and wherein the plurality of thermalconductive elements is more dense at a central area of the transducerthan at a peripheral area of the transducer.
 64. The composite structureof claim 63, wherein the plurality of layers of backing material and theplurality of thermal conductive elements are bonded to form thecomposite structure.
 65. The composite structure of claim 63, whereinthe plurality of thermal conductive elements is disposed parallel to theplurality of layers of backing material.
 66. The composite structure ofclaim 63, wherein the plurality of points on the composite structure ofbacking material comprises one or more sides of the composite structureof backing material.
 67. The composite structure of claim 63, whereinthe plurality of points on the composite structure of backing materialcomprises a rear side of the composite structure of backing material.68. The composite structure of claim 63, wherein the backing materialcomprises an epoxy material.
 69. The composite structure of claim 63,wherein a thickness of each of the plurality of layers of backingmaterial is in a range from about 0.2 mm to about 2.0 mm.
 70. Thecomposite structure of claim 63, wherein the plurality of thermalconductive elements comprises a metal foil.
 71. The composite structureof claim 70, wherein the metal foil is selected from the groupconsisting of a copper foil, an aluminum foil, and alloys orcombinations thereof.
 72. The composite structure of claim 63, whereinthe plurality of thermal conductive elements comprises a conductivenon-metal.
 73. The composite structure of claim 72, wherein theconductive non-metal comprises at least one of a pyrolytic graphite anda boron nitride.
 74. The composite structure of claim 63, wherein theplurality of thermal conductive elements is selected from the groupconsisting of wires, rods, flexible circuit traces, and combinationsthereof.
 75. The composite structure of claim 63, wherein a thickness ofthe plurality of thermal conductive elements is in a range from about0.01 mm to about 0.04 mm.
 76. The composite structure of claim 63,wherein a pitch between thermal conductive elements in the compositestructure is in a range of about 0.2 mm to about 2.0 mm.
 77. Atransducer assembly comprising: a plurality of transducer elementsdisposed in a first layer having a first front face and a first rearface; and an absorber disposed in a second layer having a second frontface and a second rear face, wherein the absorber is disposed adjacentto the first rear face and is acoustically coupled to the first rearface, wherein the absorber comprises a composite structure of backingmaterial having thermal conductive elements dispersed therethrough, andwherein the plurality of thermal conductive elements is more dense at acentral area of the transducer than at a peripheral area of thetransducer.
 78. The assembly of claim 77, further comprising a thermalconductive structure coupled to the composite structure of backingmaterial, wherein the thermal conductive structure is configured toprovide a thermal path from the composite structure of backing materialto a heat dissipating structure.
 79. The assembly of claim 78, whereinthe thermal conductive structure comprises a metal sheet extending froma plurality of sides of the composite structure to an inside surface ofa probe handle.
 80. The assembly of claim 79, wherein the metal sheetcomprises a copper sheet.
 81. The assembly of claim 78, wherein thethermal conductive structure comprises a cooling system, wherein thecooling system is configured to transfer heat from the compositestructure to a heat dissipating structure via a transducer cable. 82.The assembly of claim 77, wherein the composite structure of backingmaterial comprises a plurality of layers of backing materialalternatingly arranged between a plurality of thermal conductiveelements, wherein the plurality of thermal conductive elements areconfigured to transfer heat from a center of the transducer to aplurality of points on the composite structure of backing material. 83.The assembly of claim 82, wherein the plurality of layers of backingmaterial and the plurality of thermal conductive elements are bonded toform the composite structure.
 84. The assembly of claim 82, wherein theplurality of thermal conducting elements is disposed parallel to theplurality of layers of backing material.
 85. An ultrasound system, thesystem comprising: an acquisition subsystem configured to acquireultrasound data, wherein the acquisition subsystem comprises at leastone transducer assembly, wherein the transducer assembly comprises acomposite structure of backing material having thermal conductiveelements dispersed therethrough, and wherein the plurality of thermalconductive elements is more dense at a central area of the transducerthan at a peripheral area of the transducer; and a processing subsystemconfigured to process the ultrasound data acquired via the acquisitionsubsystem.
 86. The ultrasound system of claim 85, wherein theacquisition subsystem comprises at least one transducer assemblyconfigured to facilitate the acquisition of the ultrasound data.
 87. Theultrasound system of claim 86, wherein the at least one transducerassembly comprises a plurality of transducer elements disposed in afirst layer having a first front face and a first rear face, an absorberdisposed in a second layer having a second front face and a second rearface, wherein the absorber is disposed adjacent to the first rear face,and wherein the absorber comprises a composite structure of backingmaterial having conductive elements dispersed therethrough.
 88. Theultrasound system of claim 87, further comprising a disposing a thermalconductive structure, wherein the thermal conductive structure isconfigured to provide a thermal path from the composite structure ofbacking material to a heat dissipating structure.
 89. The ultrasoundsystem of claim 88, wherein the thermal conductive structure comprises ametal sheet extending from a plurality of sides of the compositestructure to an inside surface of a probe handle.
 90. The ultrasoundsystem of claim 89, wherein the metal sheet comprises a copper sheet.91. The ultrasound system of claim 88, wherein the thermal conductivestructure comprises a cooling system, wherein the cooling system isconfigured to transfer heat from the composite structure to a heatdissipating structure via a transducer cable.
 92. The ultrasound systemof claim 87, wherein the absorber comprises a plurality of layers ofbacking material alternatingly arranged between a plurality of thermalconductive elements, wherein the plurality of thermal conductiveelements are configured to transfer heat from a center of the transducerto a plurality of points on the composite structure of backing material.93. The ultrasound system of claim 92, wherein the plurality of layersof backing material and the plurality of thermal conductive elements arebonded to form the composite structure.
 94. The ultrasound system ofclaim 85, comprising a display module configured to display theprocessed ultrasound data.
 95. The ultrasound system of claim 85,comprising a user interface configured to enable an operator to acquireand/or display the ultrasound data.
 96. The ultrasound system of claim85, comprising a data repository module configured to store theultrasound data.
 97. The ultrasound system of claim 85, comprising animaging workstation module configured to manipulate the ultrasound data.